Hello troy,
To offer another point of view I think you will find that ALL free content is overused. No matter what you do it's best to purchase your own content sets and most of all "try to be original". Think out of the box and do your own thing. Maybe throw new things at the surfer that they may not have seen before.
It can be a good idea to view each of your sites as a investment.
A $15 - $25 picture set will pay for itself with your first sale. Plus... having your own content and being original will provide better opportunities to be listed with all the link list, etc...
A last point of view is that with free content that has been already seen by the surfer will not give the surfer any incentive for sticking around your site. Once they first see what you have it will probably end up being a quick click out and therefore no sale.
Presenting the surfer with fresh content will keep them around long enough for you to present them with your advertising.
Good luck with all your future ventures.
It's nice seeing you asking good questions and putting for the effort to get input and guidance from other experienced webmasters.